radiolytic synthesis of pt-ru catalysts based on functional

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2011, Article ID 134721, 8 pagesdoi:10.1155/2011/134721

Research Article

Radiolytic Synthesis of Pt-Ru Catalysts Based onFunctional Polymer- Grafted MWNT and Their CatalyticEfficiency for CO and MeOH

Dae-Soo Yang, Kwang-Sik Sim, Hai-Doo Kwen, and Seong-Ho Choi

Department of Chemistry, Hannam University, Daejeon 305-811, Republic of Korea

Correspondence should be addressed to Seong-Ho Choi, [email protected]

Received 12 April 2010; Revised 4 June 2010; Accepted 23 June 2010

Academic Editor: William W. Yu

Copyright © 2011 Dae-Soo Yang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Pt-Ru catalysts based on functional polymer-grafted MWNT (Pt-Ru@FP-MWNT) were prepared by radiolytic deposition of Pt-Ru nanoparticles on functional polymer-grafted multiwalled carbon nanotube (FP-MWNT). Three different types of functionalpolymers, poly(acrylic acid) (PAAc), poly(methacrylic acid) (PMAc), and poly(vinylphenyl boronic acid) (PVPBAc), were graftedon the MWNT surface by radiation-induced graft polymerization (RIGP). Then, Pt-Ru nanoparticles were deposited onto the FP-MWNT supports by the reduction of metal ions using γ-irradiation to obtain Pt-Ru@FP-MWNT catalysts. The Pt-Ru@FP-MWNTcatalysts were then characterized by XRD, XPS, TEM ,and elemental analysis. The catalytic efficiency of Pt-Ru@FP-MWNT catalystwas examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC). The Pt-Ru@PVPBAc-MWNTcatalyst shows enhanced activity for electro-oxidation of CO and MeOH oxidation over that of the commercial E-TEK catalyst.

1. Introduction

Although carbon-supported Pt-Ru nanoparticles (Pt-Ru/C)are known to be the best anode catalysts for direct methanolfuel cell (DMFC), They are still insufficient for the commer-cial application. Many researcher efforts have been devoted toimproving the catalytic performance of Pt-Ru/C by catalystdispersion [1–3]. In previous paper, we deposited Pt-Runanoparticles on the surface of the various carbon supports,including Vulcan XC-71, Ketjen-300, Ketjen-600, SWNTs,and MWNTs for use as fuel cell catalysts [4]. However,the metallic alloy nanoparticles were aggregated on thesurface of the carbon supports due to their hydrophobicnature. The metal (Ag or Pd) and alloy (Pt-Ru) nanoparticleswere also deposited on the surface of single-walled carbonnanotubes (SWNTs) [5], and porous carbon supports usingγ-irradiation without protecting agents [6]. Silva et al. [7]reported the preparation of Pt-Ru/C electrocatalysts usingγ-irradiation in water/ethylene glycol. This paper showedthe patterns of Pt-Ru nanoparticles on carbon supports;however, it did not indicate the catalytic efficiency of MeOHoxidation based on the aggregation degree. It is proposed that

the catalytic efficiency is affected by the metallic nanoparticleaggregation degree on carbon supports.

To overcome the aggregation of the metallic nanopar-ticles, the carbon support surface was modified withhydrophobic properties to obtain hydrophilic properties byin-situ polymerization of β-caprolactone, methacrylate, andpyrrole using oxidizing agents as the initiator [8]. Pt-Runanoparticles were then deposited on the polymer-wrappedMWNT supports to produce a direct methanol fuel cell(DMFC) catalyst. Pt-Ru at poly(pyrrole)-MWNT catalystsobtained high catalytic efficiency for CO stripping andmethanol oxidation. The surface of MWNTs was then coatedusing conductive polymers such as aniline, pyrrole, andthiophene to go from hydrophobic properties to hydrophilicproperties [9]. Finally, the metallic nanoparticles weredeposited on conducting polymer-wrapped MWNTs. How-ever, the prepared Pt-Ru catalysts provided lower catalyticefficiency compared to that of commercial E-TEK catalyst.

Radiation-induced graft polymerization (RIGP) is auseful method for the introduction of functional groupsonto different polymer materials using specially selectedmonomers. There have been several reports about RIGP

2 Journal of Nanomaterials

of polar monomers onto polymer subtracts to obtainhydrophilic properties for versatile applications [10–14].The RIGP method can easily functionalize the surface ofMWNTs to the desired properties. In a previous paper,we described the functionalization of MWNTs by RIGP ofderivatives vinyl monomers and their application in enzyme-free biosensors [15]. However, little has been reported aboutthe deposition of Pt-Ru nanoparticles on the functionalizedMWNT supports by γ-irradiation for DMFC catalysts.

In this study, Pt-Ru nanoparticles were deposited onthe functional polymer (FP)-grafted MWNT obtained fromRIGP using γ-irradiation to produce an anode catalyst forDMFCs. The obtained Pt-RuatFP-MWNT catalysts werecharacterized by XRD, XPS, TEM, and elemental analysis.Furthermore, the catalytic efficiency of the Pt-RuatFP-MWNT catalyst was evaluated for CO stripping and MeOHoxidation for use in a DMFC and compared to the catalyticefficiency of the commercial E-TEK catalyst.

2. Experimental

2.1. Chemicals. H2PtCl6 ×H2O (37.5% Pt), RuCl3×H2O(41.0% Ru), acrylic acid (AAc), methacrylic acid (MAc),and 4-vinylphenylboronic acid (VPBAc) were of analyticalreagent grade (Sigma-Aldrich, USA) and used withoutfurther purification. MWNTs (CM-95) were supplied byHanwha Nanotech Co., Ltd (Korea). The commercial E-TEKcatalyst (metallic content, 30 wt-%) was purchased from E-TEK (BASF Fuel Cell Inc., NJ, USA). Nafion (perflourinatedion-exchange resin, 5% (w/v) solution in a solution of 90%aliphatic alcohol/10% water mixture) was also purchasedfrom Sigma-Aldrich (USA). Solutions for the experimentswere prepared with water purified in a Milli-Q puls waterpurification system (Millipore Co. Ltd. USA), the finalresistance of water was 18.2 MΩcm−1 and degassed prior toeach measurement. Other chemicals were of reagent grade.

2.2. RIGP of Functional Monomers on the Surface of MWNTs.MWNTs were purified to remove the catalyst and noncrystal-lized carbon impurities with phosphoric acid solution. Thepurified MWNTs were used as the supporting materials forgrafting of various vinyl monomers. The MWNTs (2.0 g)and AAc (2.0 g) were then mixed in aqueous solution(20 mL). Nitrogen gas was bubbled through the solutionfor 30 minutes to remove oxygen gas, and the solution wasirradiated from a Co-60 source under atmospheric pressureand ambient temperature. A total irradiation dose of 30 kGy(dose rate = 6.48 × 105/h) was used. The other functionalpolymer-grafted MWNTs were prepared using a similarprocedure.

2.3. Preparation of Pt-RuatFP-MWNT Catalysts by γ-Irradiation. The Pt-RuatPVPBAc-MWNT catalysts wereprepared as follows: H2PtCl6×H2O (0.43 g) and RuCl3×H2O (0.41 g) were dissolved in deionized water (188 mL)in 2-propanol (12.0 mL) as the radical scavenger. 1.00 g ofPVPBAc-MWNT support was added to the above solution.Nitrogen was bubbled for 30 min through the solutionto remove oxygen and then irradiated under atmospheric

pressure and ambient temperature. A total irradiation doseof 30 kGy (a dose rate = 6.48 × 105/h) was applied. Pt-Runanoparticle-deposited PVPBAc-MWNT catalysts were pre-cipitated after γ-irradiation. The Pt-RuatPAAc-MWNT andPt-RuatPMAc-MWNT catalysts were prepared as describedabove.

2.4. Characteristics of Pt-RuatFP-MWNT Catalysts. Particlesize and morphology of the Pt-RuatFP-MWNT catalystswere analyzed by HR-TEM (JEOL, JEM-2010, USA). Thecontent of Pt and Ru in samples was analyzed by inductivelycoupled plasma-atomic emission spectrometer (ICP-AES)(Jobin-Yvon, Ultima-C, USA). X-ray diffraction (XRD)patterns for samples were obtained using a Japanese RigakuD/max γA X-ray diffractometer equipped with graphitemonochromatized Cu Ka radiation (l = 0.15414 nm). Thescanning range was 5–80◦ with a scanning rate of 5◦/min.

To evaluate the catalytic efficiency of Pt-RuatFP-MWNTcatalysts for the electro-oxidation of CO and MeOH, the Pt-RuatFP-MWNT-coated electrode was prepared as follows.Firstly, the catalytic inks were prepared by mixing of Pt-RuatFP-MWNT catalysts (5.0 mg) and 5% Nafion solution(0.05 mL) and stirred for 24 hrs. Secondly, the catalytic inkswere applied on a glass carbon (0.02 cm2) by wet coating anddried in a vacuum oven at 50◦C under nitrogen gas. Theelectro-oxidation of CO and MeOH (1.0 M) was examinedusing the Pt-RuatFP-MWNT catalyst electrode, submergedin 0.5 M H2SO4 electrolyte by cyclic voltammetry (EG&GInstruments, Potentiostat/Galvanostat model 283, USA) atscan rate of 100 mV/s. All the measurements were carried outat room temperature.

3. Results and Discussion

3.1. Radiolytic Preparation of Pt-RuatFP-MWNT Catalystsand Its Characterization. Pt-RuatFP-MWNT catalysts wereprepared by radiolytic reduction of metallic ions in water/2-propanol solution in the presence of FP-MWNT supportsat room temperature. When γ-ray irradiated in aqueoussolutions, various species were generated, as shown in thefollowing equation [16]:

H2O −→ e−aq, H+, H·, OH·, H2O2, H2 (1)

Among them, the solvated electrons, e−aq and H· radicalscan be used as strong reducing agents. The metal ions werereduced to the zero-valent state as shown in the following:

M+ + e−aq −→ M0

M+ + H· −→ M0 + H+(2)

Similarly, multivalent ions, such as Pt4+ and Ru3+, arereduced by a multistep reaction. On the other hand, thehydroxyl radical (OH·) can be oxidized for the ions or zero-valence metal atom. In order to protect the oxidizing agent(OH·), 2-propanol was added to the reaction solution. TheOH· radical was reacted with 2-propanol as shown in (3). As

Journal of Nanomaterials 3

50 nm

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Figure 1: TEM images of the Pt-RuatMWNT (a),Pt-RuatPAAc-MWNT (b), Pt-RuatPMAc-MWNT (c) and Pt-RuatPVPBAc-MWNT (d)catalyst prepared by γ-irradiation.

results, the metal ion was then reduced to zero-valence metalatom by 2-propanol radical as shown in the following.

(CH3)2CHOH + ·OH −→ (CH3)2C·OH + H2O

M+ + (CH3)2C·OH −→ M0 + (CH3)2C = O + H+

(3)

Figure 1 shows the TEM images of the Pt-RuatMWNT(a), Pt-RuatPAAc-MWNT (b), Pt-RuatPMAc-MWNT (c),and Pt-RuatPVPBAc-MWNT (d) catalysts prepared by γ-irradiation. As shown in Figure 1(a), there are no Pt-Ru nanoparticles on the surface of MWNT, whereas largeamounts of Pt-Ru nanoparticles are shown on the surfaceof FP-MWNT supports, Figures 1(b), 1(c), and 1(d). Largeamounts of Pt-Ru nanoparticles were successfully loaded onthe surface of FP-MWNT. The mean particle sizes of thePt-Ru nanoparticle on the surface of PAAc-MWNT, PMAc-MWNT, and PVPBAc-MWNT supports were in the rangeof 2.5–4.0 nm, 5.0–7.5 nm, and 2.0–2.5 nm, respectively. Onthe other hand, the commercial E-TEK catalyst showed amean particle size of 2.5 ± 0.7 nm [17]. As shown in theTEM image, the Pt-Ru nanoparticles were well dispersed onthe surface of FP-MWNT supports because the surface ofcarbon is changed from hydrophobic property to hydrophilicproperty. The property of metallic nanoparticles was alsopossessed as hydrophilic property. Thus, these catalysts areexpected to have good efficiency for methanol oxidation.

To clarify the chemical state of Pt-Ru nanoparticlesdeposited on FP-MWNTs, X-Ray photoelectron spectro-scopy (XPS) measurements were taken. Figure 2 shows theregional Pt4f and Ru3p XPS spectra of Pt-RuatPAAc-MWNT(a), Pt-RuatPMAc-MWNT (b), and Pt-RuatPVPBAc-MWNT catalyst (c) prepared by γ-irradiation. The Pt4f

peaks of the catalysts appeared about 72 eV and 75 eV dueto metallic Pt and Pt(IV)O2, respectively. Li and Hsing[18] reported that the Pt4f XPS signal was appeared intothree components with respective binding energies of 71.8,72.9, and 74.6 eV. It was concluded that these signals wereattributed to the metallic Pt, Pt(II)O, and Pt(IV)O2 species.On the other hand, the Ru3p1/2 and Ru3p3/2 peaks for thePt-RuatPAAc-MWNT and Pt-RuatPMAc-MWNT wereshown at 486 eV and 463 eV, respectively. The 463 eV signalsare due to metallic Ru(0). Li and Hsing [18] interpreted463 eV signal due to Ru(0) and RuO2. In Figure 2(c), theRu3p signals of Pt-RuatPVPBAc-MWNT catalysts wereshifted onto the large binding energy compared to that ofPt-RuatPAAc-MWNT and Pt-RuatPMAc-MWNT. It maybe considered that the hydrous ruthenium oxide, RuOxHy,was produced from the reaction of boronic acid group of thegrafted PVBAc onto MWNT during γ-irradiation. However,a further investigation is needed to clarify these signals.

Figure 3 shows the X-ray diffraction patterns of thePt-RuatFP-MWNT catalysts prepared by γ-irradiation. Allsamples showed the peak at about 20◦, which was associated


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Figure 2: X-ray photoelectron spectroscopy (XPS) spectra of Pt and Ru on Pt-RuatPAAc-MWNT (a), Pt-RuatPMAc-MWNT (b) and Pt-RuatPVBAc-MWNT catalyst (c) prepared by γ-irradiation.


Table 1: Contents of Pt-Ru on the prepared catalyst(a).

Catalysts Ptcontent(wt-%)

Ru content(wt-%)

Pt-Ru at MWNT ND ND

Pt-Ru at PAAc-MWNT 8.77 10.8

Pt-Ru at PMAc-MWNT 8.20 9.98

Pt-Ru at PVPBAc-MWNT 11.2 6.01

E TEK cataylst(30 wt-%) 21.6 10.5(a)

Metal content (wt-%) was determined by ICP-AES.

to the MWNT supporting material. The crystallinity of Pt-Ru catalysts was confirmed by the presence of peaks around39.9◦, 46.2◦, and 67.4◦. These peaks are assigned as Pt(111),(200) planes, and (220), respectively, of the face-centeredcubic (fcc) structure of platinum and platinum alloy particles[19]. The XRD peaks corresponding to metallic rutheniumwith hexagonal structure were not detected for these samples.The average particle size of the Pt-Ru catalysts can becalculated via XRD patterns according to Scherrer’s formula[20, 21].

dXRD = 0.9λβ1/2 cos θ

, (4)

where dXRD is the average particle size (nm) λ is thewavelength of the x-ray (0.15406 nm) θ is the angle at thepeak maximum β1/2 is the width (radians) of the peak athalf height. The calculated mean sizes from the diffractionpeak of Pt(111) are as follows: 3.2 nm in Figure 3(a), 3.1 nmin Figure 3(b), and 2.9 nm in Figure 3(c). There are no sizechanges of Pt-Ru catalyst on various functionalized polymer-grafted MWNT. This behavior may show that the growthof nanoparticles is prevented via dimethylketone during γ-irradiation, as shown in (5).

Table 1 shows the content (wt-%) of Pt and Ru elementsin the Pt-RuatFP-MWNT catalysts. In ICP-AES results ofthe Pt-RuatFP-MWNT catalyst, the Pt element content (wt-%) in the Pt-RuatPAAc-MWNT, Pt-RuatPMAc-MWNT, andPt-RuatPVPBAc-MWNT catalysts was determined as 8.77%,8.20%, and 11.20% for all that addition of 16.125% inreaction mixture, respectively. While Ru element contentin the Pt-RuatPAAc-MWNT, Pt-RuatPMAc-MWNT, andPt-RuatPVPBAc-MWNT catalysts was obtained as 10.8%,9.98%, and 6.01%, for all that addition of 16.81% in reactionmixture, respectively. In the case of Pt-RuatPVPBAc-MWNTcatalyst, the Pt content is higher than that of the othercatalysts. In commercial E-TEK catalyst, the Pt content ishigher than Ru content, as shown in Table 1.

3.2. Catalytic Efficiency of Pt-RuatFP-MWNT Catalyst for COand MeOH. To find the catalytic efficiency of Pt-RuatFP-MWNT catalysts, they were tested for the electrochemicaloxidation of carbon monoxide (CO). Figure 4 shows thecyclic voltammograms (CVs) of electro-oxidation of COfor Pt-RuatFP-MWNT catalyst prepared by γ-irradiation

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Figure 3: XRD spectra of Pt-RuatPAAc-MWNT (a), PT-Ruat-PMAc-MWNT (b), and Pt-RuatPVPBAc-MWNT (c) catalyst forDMFC.


Pt-Ru@PAAc-MWNTs

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between E-TEK the catalyst and the prepared catalyst. (a) E-TEKcatalyst versus Pt-RuatPAAc-MWNT catalyst, (b) E-TEK catalystversus Pt-RuatPMAc-MWNT, (c) E-TEK versus Pt-RuatPVPBAc-MWNT.

in 0.5 M H2SO4: (a) RuatPAAc-MWNT, (b) Pt-RuatPMAc-MWNT, and (c) Pt-RuatPVPBAc-MWNT catalyst. To com-pare CO adsorption efficiency, it was measured and com-pared to the commercial E-TEK catalyst containing 30 wt-% Pt on carbon. The higher CO stripping peak at thecommercial E-TEK catalyst electrode is more apparent thanthat of the Pt-RuatPAAc-MWNT and Pt-RuatPMAc-MWNTcatalyst electrodes, as shown in Figures 4(a) and 4(b). How-ever, the measured CO stripping peak at Pt-RuatPVPBAc-MWNT catalyst electrode is significantly higher than that ofthe commercial E-TEK electrode in spite of the metal catalystin high amount as shown in Figure 4(c). A significant currentdensity is noticed at the Pt-RuatPVPBAc-MWNT catalystelectrodes for the CO oxidation starting from 0.72 V. Theelectrochemically active specific area (SEAS) of the catalystswas calculated using the charges deduced from the CV ofCO adsorption and desorption electro-oxidation process andusing (5) [22].

SEAS = QCO

G× 420, (5)

where QCO is the charge for CO desorption electro-oxidationin microcolumb (μC); G represents the summation ofPt + Ru metals loading (μg) in the electrode, and 420is the charge required to oxidize a monolayer of CO onthe catalysts in μC cm−2. The electrochemical SEASs are60 m2 g−1 for the commercial E-TEK catalysts. In the caseof the prepared catalysts, the electrochemical SEASs are34, 30, and 126 m2 g−1 for the Pt-RuatPAAc-MWNT, Pt-RuatPMAc-MWNT, and Pt-RuatPVPBAc-MWNT catalysts,respectively. The SEAS of Pt-RuatPVPBAc-MWNT catalystsprepared by γ-irradiation are higher than that of commercialE-TEK catalysts due to hydrous ruthenium oxide. It mightbe based on the promotion of CO oxidation on Pt atomsby the second metal (Ru) which provides OH-type species,the more oxidizable second metal, thus promotes catalyticactivities.

Figure 5 shows the cyclic voltammograms of E-TEKcatalyst and the prepared catalysts for 1.0 M MeOH oxidationin 0.5 M H2SO4 at room temperature. The higher currentpeak at about 0.6 V versus Ag/AgCl electrode appeared dueto methanol oxidation on the commercial E-TEK catalyst, asshown in Figures 5(a), 5(b), and 5(c). However, the methanoloxidation peak for Pt-RuatPAAc-MWNT catalyst and Pt-RuatPMAc-MWNT catalyst were lower than that of the E-TECK catalyst, as shown in Figures 5(a) and 5(b). In thecase of Pt-RuatPVPBAc-MWNT catalyst, the large catalyticefficiency at 0.8 V was observed. As a result, the preparedPt-RuatPVPBAc-MWNT catalyst can be used on a directmethanol fuel cell electrode.

4. Conclusion

The functionalized MWNTs were prepared by radiation-induced graft polymerization of vinyl monomers with thedesired functional group. Subsequently, Pt-Ru nanoparticleswere deposited on the surface of the functionalized MWNTfor using as a fuel cell-electrode catalyst. The efficiency


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Figure 5: Comparison of catalytic efficiency among E-TEK catalystand the prepared catalysts for MeOH oxidation in 0.5 M H2SO4.E-TEK catalyst versus Pt-RuatPAAc-MWNT catalyst, (b) E TEKcatalyst versus Pt-RuatPMAc-MWNT catalyst, and (c) E-TEKcatalyst versus Pt-RuatPVPBAc-MWNT.

of the prepared catalysts was investigated. The followingconclusions are based on the results.

(1) The catalytic efficiency of Pt-RuatPVPBAc-MWNTcatalyst for CO stripping was higher than that ofthe commercial E-TECK catalyst in spite of the lowmetallic content.

(2) The stripping voltammograms for the adsorbed COat Pt-RuatPVPBAc-MWNT catalyst prepared by γ-irradiation reveal that the CO oxidation is energeti-cally favorable at these electrodes.

(3) The MeOH oxidation peak appeared at 0.8 V onPt-RuatPVPBAc-MWNT catalyst prepared by γ-irradiation which appears to be suitable for theelectrode assembly in direct methanol fuel cells.

Acknowledgments

This paper was supported by Nano R&D program andNational Nuclear Technology program through the KoreaScience and Engineering Foundation funded by the Ministryof Science & Technology. The authors particularly thank theKorea Basic Science Institute (KBSI) for FETEM measure-ments.

References

[1] B. Yang, Q. Lu, Y. Wang et al., “Simple and low-costpreparation method for highly dispersed PtRu/C catalysts,”Chemistry of Materials, vol. 15, no. 18, pp. 3552–3557, 2003.

[2] Z. Liu, X. Y. Ling, X. Su, and J. Y. Lee, “Carbon-supportedPt and PtRu nanoparticles as catalysts for a direct methanolfuel cell,” Journal of Physical Chemistry B, vol. 108, no. 24, pp.8234–8240, 2004.

[3] G. Girishkumar, K. Vinodgopal, and P. V. Kamat, “Carbonnanostructures in portable fuel cells: single-walled carbonnanotube electrodes for methanol oxidation and oxygenreduction,” Journal of Physical Chemistry B, vol. 108, no. 52,pp. 19960–19966, 2004.

[4] S.-D. Oh, K. R. Yoon, S.-H. Choi et al., “Dispersion of Pt-Ru alloys onto various carbons using γ-irradiation,” Journalof Non-Crystalline Solids, vol. 352, no. 4, pp. 355–360, 2006.

[5] S.-D. Oh, B.-K. So, S.-H. Choi et al., “Dispersing of Ag, Pd, andPt-Ru alloy nanoparticles on single-walled carbon nanotubesby γ-irradiation,” Materials Letters, vol. 59, no. 10, pp. 1121–1124, 2005.

[6] K.-D. Seo, S.-D. Oh, S.-H. Choi, S.-H. Kim, H. G. Park, and Y.P. Zhang, “Radiolytic loading of the Pt-Ru nanoparticles ontothe porous carbons,” Colloids and Surfaces A, vol. 313-314, pp.393–397, 2008.

[7] D. F. Silva, A. O. Neto, E. S. Pino, M. Linardi, and E. V. Spinace,“PtRu/C electrocatalysts prepared using γ-irradiation,” Jour-nal of Power Sources, vol. 170, no. 2, pp. 303–307, 2007.

[8] H.-B. Bae, J.-H. Ryu, B.-S. Byun, S.-H. Choi, S.-H. Kim, andC.-G. Hwang, “Radiolytic deposition of Pt-Ru catalysts onthe conductive polymer coated MWNT and their catalyticefficiency for CO and MeOH,” Advanced Materials Research,vol. 47–50, part 2, pp. 1478–1481, 2008.

[9] H.-B. Bae, S.-H. Oh, J.-C. Woo, and S.-H. Choi, “Preparationof Pt-Ru@PPy-MWNT catalysts by γ-irradiation and chemical


reduction and their adsorption capacity for CO,” JournalNanoscience and Nanotechnology, vol. 10, pp. 6901–6906, 2010.

[10] S.-H. Choi, Y. C. Nho, and G.-T. Kim, “Adsorption of Pb2+

and Pd2+ on polyethylene membrane with amino group mod-ified by radiation-induced graft copolymerization,” Journal ofApplied Polymer Science, vol. 71, no. 4, pp. 643–650, 1999.

[11] S.-H. Choi and Y. C. Nho, “Adsorption of Co2+ by stylene-g-polyethylene membrane bearing sulfonic acid groups modi-fied by radiation-induced graft copolymerization,” Journal ofApplied Polymer Science, vol. 71, no. 13, pp. 2227–2235, 1999.

[12] S.-H. Choi and Y. C. Nho, “Adsorption of UO2+2 by

polyethylene adsorbents with amidoxime, carboxyl, and ami-doxime/carboxyl group,” Radiation Physics and Chemistry, vol.57, no. 2, pp. 187–193, 2000.

[13] S.-H. Choi and Y. C. Nho, “Radiation-induced graft copoly-merization of binary monomer mixture containing acry-lonitrile onto polyethylene films,” Radiation Physics andChemistry, vol. 58, no. 2, pp. 157–168, 2000.

[14] S.-H. Choi, K.-P. Lee, and J.-G. Lee, “Adsorption behavior ofurokinase by polypropylene film modified with amino acidsas affinity groups,” Microchemical Journal, vol. 68, no. 2-3, pp.205–213, 2001.

[15] D.-S. Yang, D.-J. Jung, and S.-H. Choi, “One-step function-alization of multi-walled carbon nanotubes by radiation-induced graft polymerization and their application as enzyme-free biosensors,” Radiation Physics and Chemistry, vol. 79, no.4, pp. 434–440, 2010.

[16] J. Belloni, M. Mostafavi, H. Remita, J.-L. Marignier, and M.-O.Delcourt, “Radiation-induced synthesis of mono- and multi-metallic clusters and nanocolloids,” New Journal of Chemistry,vol. 22, no. 11, pp. 1239–1255, 1998.

[17] A. O. Neto, T. R. R. Vasconcelos, R. W. R. V. da Silva, M.Linardi, and E. V. Spinace, “Electro-oxidation of ethyleneglycol on PtRu/C and PtSn/C electrocatalysts prepared byalcohol-reduction process,” Journal of Applied Electrochem-istry, vol. 35, no. 2, pp. 193–198, 2005.

[18] X. Li and I.-M. Hsing, “Surfactant-stabilized PtRu colloidalcatalysts with good control of composition and size formethanol oxidation,” Electrochimica Acta, vol. 52, no. 3, pp.1358–1365, 2006.

[19] M. Tsuji, M. Kubokawa, R. Yano et al., “Fast preparationof PtRu catalysts supported on carbon nanofibers by themicrowave-polyol method and their application to fuel cells,”Langmuir, vol. 23, no. 2, pp. 387–390, 2007.

[20] Y. Shao, G. Yin, Y. Gao, and P. Shi, “Durability study of PtC andPtCNTs catalysts under simulated PEM fuel cell conditions,”Journal of the Electrochemical Society, vol. 153, no. 6, pp.A1093–A1097, 2006.

[21] S. Kim and S.-J. Park, “Effects of chemical treatment of carbonsupports on electrochemical behaviors for platinum catalystsof fuel cells,” Journal of Power Sources, vol. 159, no. 1, pp. 42–45, 2006.

[22] A. Pozio, M. de Francesco, A. Cemmi, F. Cardellini, and L.Giorgi, “Comparison of high surface Pt/C catalysts by cyclicvoltammetry,” Journal of Power Sources, vol. 105, no. 1, pp. 13–19, 2002.

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